The present disclosure claims priority to U.S. Provisional Patent Application Ser. No. 60/956,419, filed Aug. 17, 2007.
The present disclosure relates to aircraft operations in a degraded visual environment.
Rotary wing aircraft are routinely required to approach and land at remote sites without external navigational guidance or acceptable visual conditions. Often the topography, ground hazards, mobile obstacles, stationary objects and weather in the area are unknown or changing. Upon arrival at the remote site, the pilot must typically make critical judgments based on incomplete or inaccurate data in order to determine the proper procedure to approach and land. If the terrain condition is such that dust, snow, sand, or the like will be stirred by rotor downwash, the rotary wing aircraft may become engulfed in a cloud of visually-restrictive material. This is commonly referred to as a degraded visual environment (DVE) or a “brownout/whiteout.”
Research including literature reviews, pilot interviews, and military incident reports indicate that incidents due to DVE conditions often occur because the pilot becomes spatially disoriented due to loss of visual references. During approach to hover and landing, the pilot manipulates the aircraft controls to conduct a constant deceleration of ground velocity while coordinating a rate of descent to the ground in such a way as to arrive at the ground with little or no forward velocity and a low rate of descent. In addition to controlling a rate of descent, the pilot must also compensate for forward, aft, lateral, and heading drift.
The approach to landing in DVE conditions is visually intensive. In a DVE approach where the outside environment is obscured, the pilot's ability to visually establish the approach profile and maintain stable flight is dramatically affected.
Although rotary wing aircraft are effectively operated in DVE conditions, systems for enhanced DVE operations are desired.